From: Paulo Alcantara <pc@cjr.nz>
Date: Thu, 27 Aug 2020 11:20:19 -0300
Subject: [PATCH] cifs: fix check of tcon dfs in smb1
Git-commit: e183785f2529b4135f00a0330a3b08e7c86530c8
Patch-mainline: v5.9-rc3
References: bsc#1178270

For SMB1, the DFS flag should be checked against tcon->Flags rather
than tcon->share_flags.  While at it, add an is_tcon_dfs() helper to
check for DFS capability in a more generic way.

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Shyam Prasad N <nspmangalore@gmail.com>
Acked-by: Aurelien Aptel <aaptel@suse.com>

---
 fs/cifs/cifsglob.h | 15 +++++++++++++++
 fs/cifs/connect.c  |  2 +-
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index b296964b8afa6..b565d83ba89ed 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -2031,4 +2031,19 @@ static inline bool is_smb1_server(struct TCP_Server_Info *server)
 	return strcmp(server->vals->version_string, SMB1_VERSION_STRING) == 0;
 }
 
+static inline bool is_tcon_dfs(struct cifs_tcon *tcon)
+{
+	/*
+	 * For SMB1, see MS-CIFS 2.4.55 SMB_COM_TREE_CONNECT_ANDX (0x75) and MS-CIFS 3.3.4.4 DFS
+	 * Subsystem Notifies That a Share Is a DFS Share.
+	 *
+	 * For SMB2+, see MS-SMB2 2.2.10 SMB2 TREE_CONNECT Response and MS-SMB2 3.3.4.14 Server
+	 * Application Updates a Share.
+	 */
+	if (!tcon || !tcon->ses || !tcon->ses->server)
+		return false;
+	return is_smb1_server(tcon->ses->server) ? tcon->Flags & SMB_SHARE_IS_IN_DFS :
+		tcon->share_flags & (SHI1005_FLAGS_DFS | SHI1005_FLAGS_DFS_ROOT);
+}
+
 #endif	/* _CIFS_GLOB_H */
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index a275ee399dcea..392c44d64d8a6 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -4909,7 +4909,7 @@ int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *vol)
 		if (!tcon)
 			continue;
 		/* Make sure that requests go through new root servers */
-		if (tcon->share_flags & (SHI1005_FLAGS_DFS | SHI1005_FLAGS_DFS_ROOT)) {
+		if (is_tcon_dfs(tcon)) {
 			put_root_ses(root_ses);
 			set_root_ses(cifs_sb, ses, &root_ses);
 		}
-- 
2.28.0